For ease and safety of administration, many prescription and non-prescription drugs are provided in the form of capsules and tablets for oral administration. However, patients at the extremes of age, children and the elderly, often experience difficulty in swallowing solid oral dosage forms. For these patients, drugs are commonly provided in liquid dosage forms such as solutions, emulsions and suspensions. These dosage forms usually permit perceptible exposure of the active drug ingredient to the taste bud, which gives rise to another problem. Many drugs have unpleasant tastes, and in particular are often extremely bitter. As a consequence, unless measures are taken to make the liquid dosage forms palatable, patient compliance with the prescribed regimen of treatment will suffer. Measures to make liquid dosage forms palatable include a variety of approaches. The use of relatively insoluble salts of the parent drug results in less exposure of drug in perceptible form in the mouth. Suspensions of very small coated granules of the drug prevent release of the drug in the mouth and provide a taste-hiding effect. Syrups of sugar, with or without flavoring, are often sufficient to mask the taste of the drug. Nevertheless, some drugs have such pronounced bitterness or other physico-chemical characteristics that conventional approaches to flavor masking and/or hiding are unsuccessful. This is particularly problematic where the drug in question has extensive applicability in treatment of diseases of children or the elderly.
Erythromycin has a bitter taste and is particularly useful in treatment of common pediatric infections of the middle ear and upper respiratory tract, as well as certain forms of pneumonia which afflict the elderly. Acceptably palatable liquid oral dosage forms of this drug have been developed, primarily using esters and other prodrug forms of the molecule. However, such ester forms can markedly alter the pharmacokinetics and total availability of the drug in vivo. Therefore, a need exists for additional palatable oral dosage forms for erythromycin, and particularly for the base form of the drug. In addition, it has now been observed that at least one erythromycin derivative under development, 6-O-methyl erythromyin, has such pronounced bitterness that conventional approaches have been unsuccessful in development of a palatable liquid oral dosage form of this drug. Accordingly, a particular need exists for new approaches to masking or hiding the taste of bitter erythromycin derivatives.